A mobile gas-measuring device for the simultaneous detection of different pollution gases is known from DE 101 40 945 A1. Three electrochemical sensors, which are used to measure the concentrations of possible pollution gases in a gas sample, are located in a device housing. The gas concentration values measured by the sensors are processed by an evaluating unit integrated in the measuring device and outputted via a display unit. The evaluating unit checks the measured values for plausibility and for compliance with certain, preset limit values. An optical or acoustic alarm is triggered if limit values are possibly exceeded or in case of implausible measured values.
The prior-art gas-measuring device is carried by the user as a personal monitoring device, so that pollution gases are rapidly recognized in the work area. Due to the mobility of the gas-measuring device, which is normally attached directly to the clothing or the upper body, it must have the most compact housing dimensions possible and be lightweight. The capacity of the power supply unit carried by the user is limited as a result. In case of longer-lasting measurement, this has the consequence that gas measurements are performed at certain time intervals only to save power or that the sound level of alarm generators is limited.
In case of a gas-measuring device, which is arranged stationarily in the environment of a user and continuously monitors the pollution gas content in the ambient atmosphere, it is required that the power supply should make possible a long use time and that possible warning messages be communicated to the user in a clearly perceptible manner, especially in case of high background noise level. Such gas-measuring devices can be carried by the user only to a limited extent.
Consequently, two different monitoring systems are normally needed, namely, a personal monitoring device, which is carried by the user, and a stationary monitoring device, which is arranged in the work area of persons. Different measuring systems must usually be kept ready for this purpose, which increases the costs, especially due to the fact that twice the number of gas-measuring systems must be kept ready.